1. Field of the Invention
The present invention relates to a stereoscopic display apparatus and a technique to which the stereoscopic display apparatus is applied.
2. Description of the Related Art
There has been well known such a fact that a stereoscopic image obtained by a stereoscopic vision is incomparably excellent in realistic sensations and reality as compared with a normal planar image. Up to now, in order to employ the usefulness of the stereoscopic image, an attempt has been made that the application of the stereoscopic image to medical equipments, video game machines or the like becomes widespread.
In the case of applying the stereoscopic vision to the medical equipments or the video game machines, a facility has been demanded for a stereoscopic display apparatus used for giving the stereoscopic image to a viewer. Also, it is preferable that the stereoscopic display apparatus employed for the above intended purpose is of the head mount type that readily ensures the degree of freedom of viewer""s hands because the viewer is required to handle an operation appliance or manipulate a game controller.
Incidentally, the stereoscopic vision is realized by the celebration of brains using such a phenomenon that a parallax occurs in images picked up by the respective right and left eyes of the viewer. In order to realize the stereoscopic vision, there is required that image lights from the images for the respective right and left eyes with a constant parallax are supplied to the respective right and left eyes, and various display apparatuses that comply with such a requirement have been proposed.
As techniques for supplying the above image light, there have been known one technique in which the images for the respective right and left eyes are displayed on one display screen in a superimposing manner, and the image lights from the images are separated from each other by some means and given to the respective right and left eyes, and another technique in which the images for the respective right and left eyes are projected onto two display screens, respectively, and the images for the respective right and left eyes are viewed by the respectively right and left eyes, separately.
The stereoscopic display apparatus using one display screen is designed in such a manner that the images for the respective right and left eyes are projected onto one screen, the image lights from the respective images are separated and guided to the respective right and left eyes, to thereby realize the stereoscopic image. The stereoscopic display apparatus of this type is advantageous in that everybody can readily realize the stereoscopic vision because such a work that those two images are assembled into one stereoscopic image by their selves which will be described later is not required.
However, this technique makes it difficult to realize the facility and the downsizing because there is required a means for separating the image lights from the images for the respective right and left eyes which are displayed on the display screen in the superimposing fashion.
In other words, as a measure for separating the image lights which is required for the above-mentioned necessity, polarization is generally employed. The separation of polarization is implemented by, for example, a technique in which the images for the respective right and left eyes which project polarized lights different in property as image light are displayed on one screen, for example, in a time division manner, and the viewer has glasses worn.
This technique suffers from a minor problem from the viewpoint of the facility because the viewer is compelled to put on polarized glasses. Also, the stereoscopic display apparatus of that type is unavoidably liable to be complicated and large-sized because the means for separating the polarized lights is necessary.
Taking the above circumstances into consideration, the research and development of the stereoscopic display apparatuses of the head mount type which can be simply dealt with are being promoted with the application of the above-mentioned technique using two images.
The technique using two display screens is to transmit the image lights which are supplied to the respective eyes from those two display screens, separately. Therefore, since no structure for separating the lights is required, and the structure of the apparatus can be simplified, the apparatus can be readily downsized, and that technique is readily applied to the stereoscopic display apparatus of the head mount type or the like.
However, in the case of using those two display screens, the viewer is required to assemble two images naturally produced into one image by himself while viewing those two images. That is, in the technique using two display screens, the viewer does not conduct the stereoscopic vision so far as the positional relationship between those two display screens and the positional relationship between two eyes of the viewer do not satisfy very severe conditions. Therefore, this technique makes it fundamentally difficult that the viewer is allowed to conduct the stereoscopic vision.
What plays an important role in order to obtain one stereoscopic image from two images is a technique that is called xe2x80x9can inter-eye width adjustmentxe2x80x9d. Therefore, a mechanism for adjusting the width of the image lights to the width of both the right and left eyes is required for the stereoscopic display apparatus based on the above technique. This mechanism is complicated, resulting in many cases in which the apparatus becomes large-sized. Also, the above-mentioned inter-eye width adjustment does not satisfy a requirement such as the facility demanded for the video game machine because the inter-eye width adjustment cannot be executed not through miscellaneous processes such as the measurement of the inter-eye width.
Most importantly, this technique makes it difficult to conduct the stereoscopic vision, and even if the stereoscopic vision is conducted, the fatigue of the viewer is liable to become large.
The present inventors have promoted the research of the stereoscopic vision and come to the conclusion that a stereoscopic display apparatus which will be widespread as a facile and accessible apparatus.
Therefore, the present invention has been made as a result that the present inventors have promoted the research of the stereoscopic vision, and therefore an object of the present invention is to provide a stereoscopic display apparatus which is small in size and does not require the adjustment of an inter-eye width.
Another object of the present invention is to provide an endscope and a microscrope to which the above stereoscopic display apparatus is applied.
In order to achieve the above objects, according to the present invention, there is provided a stereoscopic display apparatus, comprising:
two liquid crystal devices for picking up image lights for respective right and left eyes of a viewer from an image source;
a half-mirror onto which images of the respective right and left eyes having a parallax from said two liquid crystal devices for a stereoscopic vision as a stereoscopic image are projected; and
two polarizers for the respective right and left eyes disposed between said half mirror and the respective right and left eyes of the viewer;
wherein said half-mirror operates to transmit the image lights from one of said two liquid crystal devices and to reflect the image lights from the other one of the said two liquid crystal device so that the transmitted image lights and reflected image lights are orthogonally polarized with respect to each other, and the transmitted image lights and the reflected image lights are combined and guided to said two polarizers by said half-mirror;
wherein said two polarizers for the respective right and left eyes receive the combined image lights and separate the combined image lights for the respective right and left eyes, in which one of the said polarizers shuts out the transmitted image lights in the combined image lights and allows the reflected image lights to pass through said one polarizer, and the other polarizer shuts out the reflected image lights in the combined image lights and allows the transmitted image lights to pass through said the other polarizer, and the separated image lights are given to the respective right and left eyes of the viewer to conduct the stereoscopic vision; and
wherein said liquid crystal devices, said half-mirror and said polarizers are fitted to one casing.
Since the stereoscopic display apparatus is of a type using one display screen, everybody can conduct the stereoscoptic vision and does not suffer from an excessive fatigue even in use for a long period of time. Also, since the stereoscopic display apparatus has the polarizers at a display screen side, a trouble such that the viewer puts on polarized glasses is not required.
The polarization from the half-mirror is not limited. For example, the respective polarizations for the right and left eyes may be polarized lights different in rotating direction. Also, the polarizations may be linear polarized lights having vibration planes which are orthogonal to each other. In this case, the half-mirror is designed in such a manner that the image lights of the images for the respective right and left eyes are converted into polarized lights having the vibration planes orthogonal to each.
The above-mentioned display screen may be structured as follows although it is not limited to the following structure.
That is, there are provided a half-mirror and two display devices, that control pixels for image display by using the polarization and have the vibration directions of the polarized lights angled at 45xc2x0 with respect to the half-mirror. Also, the vibration planes of the two display devices are orthogonal to each other, and one of the vibration planes becomes a transmitted light and the other vibration plane becomes a reflected light so that the images for the respective right and left eyes displayed on said display devices, respectively, are guided to said half-mirror, thereby being capable of displaying the images for the respective right and left eyes on the half mirror.
This structure is devised from the following viewpoints.
That is, in the display device such as a liquid crystal display device that controls the pixels for the image display by using the polarized lights, the image lights from the apparatus becomes naturally polarized lights. Therefore, there is the possibility that the polarized lights for the images for the respective right and left eyes in a polarized glasses system are obtained by utilizing the image lights that become naturally the polarized lights. If the polarized lights inherent to the display apparatus can be utilized, the polarizers for polarizing the image lights in the conventional polarized glasses system can be made unnecessary, and problems caused by light reduction due to the polarizers, that is, such problems that the image becomes dark, or the apparatus becomes large-sized in order to require a more intense light source can be effectively eliminated.
From the above viewpoints, the present inventors have promoted the research. As a result, the polarized light that has passed through the half-mirror does not change its vibration plane, but the polarized light reflected by the half-mirror may change its vibration direction although depending on an aspect of the vibration direction. For that reason, the present inventors have proved that the polarized lights for the images for the respective right and left eyes can be obtained even without using any polarizer. In particular, in case of the liquid crystal display apparatus, control is made in such a manner that the vibration direction of the output polarized lights is generally angled at 45xc2x0 with respect to the liquid crystal screen, and because the polarized lights that have been reflected by the half-mirror and symmetrically inverted have their vibration directions rotated by 90xc2x0, the polarized lights for the images for the respective right and left eyes are very conveniently obtained.
Accordingly, if the display apparatus such as a liquid crystal display apparatus is used in which the pixels for the image display are controlled by using the polarized lights, and the vibration directions of the polarized lights are angled at 45xc2x0 with respect to the half-mirror, one optical system for obtaining the image light for the right eye and another optical system for obtaining the image light for the left eye can be so structured as to be completely identical with each other, and therefore the structure for obtaining the display apparatus can be simplified. Also, if the display apparatus that naturally outputs the polarized light as described above is used, the polarizers required up to now for obtaining the polarized light becomes useless, and the apparatus is downsized.
The above angle of 45xc2x0 requires that one vibration plane of the polarized light reflected by the half-mirror is substantially orthogonal to the other vibration plane of the polarized light but does not require 45 accurately.
The polarizers in the stereoscopic display apparatus according to the present invention may be movable or fixed if the polarizers are fitted to the casing. If the polarizers are fixed, the stereoscopic vision can be readily conducted by viewing only the polarizers with the fixation of the-relative positions of the polarizers for the respective eyes to image optical paths in the stereoscopic display apparatus.
Also, the casing of the stereoscopic display apparatus according to the present invention may be freely shaped and structured without specific limits. The half-mirror and the polarizers for the respective right and left eyes may be exposed from the casing or may be accommodated in the interior of a hollow casing.
Further, the casing has an observation port with a hood, and the viewer can conduct the stereoscopic vision while keeping distances between the polarizers within the casing and the respective eyes of the viewer constant by pressing the periphery of the eyes against the hood by the viewer. With this operation, the viewer can more readily obtain the stereoscopic effect. That is, if the polarizers and the eyes of the viewer are apart from each other longer than a predetermined distance, the polarizers enter the visual field of the viewer, thereby making it difficult to conduct the stereoscopic vision. Therefore, the viewer makes observation while pressing the periphery of the eyes against the hood so as to keep the distances between the respective eyes of the viewer and the polarizers to the degree where the other polarizer for the eye does not enter the visual field, to thereby readily conduct the stereoscopic vision.
The casing of the stereoscopic display apparatus may be fixedly attached to a fixed substance. In the case where importance is attached to ensuring the ease of motion of a viewer""s head, it is preferable that the casing is so movable as to follow the motion of the viewer""s head. For example, the casing can be hung from a ceiling or the casing can be mounted on a movable self-sustaining stand. Also, with the provision of a wearing means for wearing the casing on the viewer""s head, the casing can be fixed to the viewer""s head in a state where the respective right and left eyes of the viewer face the observation port. With the above structure, the stereoscopic display apparatus can be used in such a state that a goggle is used, resulting in a head mount type apparatus having a small limit of the position of the viewer.
It is preferable that the stereoscopic display apparatus is equipped with a lens or a mirror which convert the images produced by the respective image lights that have passed through the polarizers for the respective right and left eyes into virtual images. The provision of the lens and the mirror makes it easier to conduct the stereoscopic vision and also makes it possible to further reduce the fatigue of the viewer.
The above-mentioned lens and mirror may be formed of one lens for both of the right and left eyes or one mirror for both of the right and left eyes. With this structure, the accuracy in the inter-eye width adjustment is not required. In other word, with the above structure, if the right and left eyes are positioned in a range where the respective image lights that have passed through the polarizers for the respective right and left eyes are guided, the stereoscopic vision is conducted even if the accurate adjustment of the inter-eye width is not conducted.
Also, the above-mentioned lens and mirror may be formed of different lenses and mirrors for the respective right and left eyes. In this case, the stereoscopic vision is not conducted if the inter-eye width adjustment is not conducted such that the pupils of the respective right and left eyes coincide with the respective centers of the lenses and the mirrors for the respective right and left eyes (the centers of the optical paths) with a predetermined precision. However, with the above operation, the lenses and the mirrors can be downsized and weight-saved.
The mirrors and the lenses equipped in the stereoscopic display apparatus may be disposed at the display screen side rather than the polarizers for the respective right and left eyes. In this case, the polarizers for the respective right and left eyes may be so arranged as to be positioned immediately before the respective eyes of the viewer. In this case, the polarizers for the respective right and left eyes may be set to be larger than the size of the respective right and left eyes.
Also, the above-mentioned display screen may be freely designed without any limit. For example, in the case of applying a time-division system, there may be used such a display apparatus that the images for the respective right and left images are alternately continuously displayed.
The half-mirror may be displayable so that the common images contained in the images for the respective right and left eyes which are displayed on the half-mirror coincide with each other.
This is based on the following knowledge that has been obtained through the research by the present inventors.
That is, according to the research of the present inventors, one cause of the viewer""s fatigue is that the common images commonly contained in the images for the respective right and left eyes which are projected onto one display screen in a superimposing manner are displaced from each other on the screen (doubly displayed). On the other hand, in case of the images for the respective right and left images which have been imaged by giving a predetermined convergent angle, even if the relative position of two images is slightly changed, the viewer can obtain the stereoscopic effect.
As a result, it is concluded that when the common images contained in the images for the respective right and left eyes are projected onto the half-mirror, if the positions of the common image on the display screen are made to coincide with each other, the stereoscopic vision is enabled, and the viewer does not suffer from the fatigue. That is, the present inventors have the knowledge that if the images for the respective right and left eyes are display in such a manner that the common image contained in the images for the respective right and left eyes coincide with each other on the half-mirror, the viewer""s fatigue can be suppressed.
It is unnecessary that the common images are made to always coincide with each other, but it is preferable that the processing is applied depending on the contents of the images for the respective right and left eyes. Also, it is possible that change-over such that the common images are made to coincide with each other or not may be conducted appropriately.
Also, the display apparatus according to the present invention is suited for the application to medical equipments such as an endscope or a microscope. According to the medical equipments of this type, in the case of conducting an operation using the endscope or an operation using a microscope, the operation can be conducted on the basis of a video with the stereoscopic effect, thereby being capable of enhancing the safety of the operation.
According to the present invention, there is provided an endscope comprising a video camera that picks up images for the respective right and left eyes with a parallax for a stereoscopic vision; and a stereoscopic display apparatus that reproduces the images for the respective right and left eyes which are supplied from the video camera to conduct a stereoscopic vision; wherein the stereoscopic display apparatus mentioned above is used as the stereoscopic display apparatus.
Also, according to the present invention, there is provided a microscope, comprising: a video camera that picks up images for the respective right and left eyes with a parallax for a stereoscopic vision; and a stereoscopic display apparatus that reproduces the images for the respective right and left eyes which are supplied from the video camera to conduct a stereoscopic vision; wherein said stereoscopic display apparatus according to the present invention is used as the stereoscopic display apparatus.